1. Field of the Invention
The present invention relates to a standard photographic lens system for single-lens reflex photographic cameras.
2. Description of the Prior Art
In Gauss type standard lens systems having aperture ratios on the order of F1.8 to F2.0, radii of curvature are generally small on the surfaces of a cemented lens component arranged on the front side of a stop or lens elements of said component arranged with an airspace therebetween and a cemented lens component arranged on the rear side of the stop. Therefore, it is possible to arrange a large number of lenses on the polishing dish in machining the above-mentioned lens elements of said type lens systems, thereby unavoidably requiring many manufacturing processes. Further, these lens elements have thin edges and can not be manufactured with high yield. Though it can be considered to select larger radii of curvature on the lens surfaces for facilitating to manufacture lens elements, large radii of curvature will aggravate asymmetry of coma. Furthermore, centering will be difficult in case where the surfaces on both sides of a lens element are to be nearly concentric. In addition, Petzval's sum will be disadvantageous when inexpensive glass materials (most of these materials have refractive indices relatively not so high) are used for manufacturing lens systems at low cost.